1. Field of the Invention
The present invention relates generally to signal converters.
2. Description of the Related Art
Multichannel signal converter systems are generally arranged in averaging configurations or in time-interleaving configurations. The first approach increases resolution without loss of speed while the second approach increases sampling rates without loss of resolution. In averaging techniques, N signal converters are clocked by a common clock signal. Output signal energy adds directly while noise sums as the root-sum-square of each output noise. As long as quantization noise is substantially greater than non-correlated noise (e.g., thermal noise), noise power is substantially reduced.
In contrast, time interleaving N signal converters increases the system sample rate by N so that the system Nyquist frequency increases by N and noise is spread over the greater bandwidth so that the noise in a specific signal bandwidth is decreased. Interleaved signal converters can substantially increase the system signal-to-noise and, unlike converter averaging, this increase is realized regardless of the noise source. A downside of time interleaving is that mismatches between the converters' gain, phase and offset generate nonharmonic spurious output signals.
Although time interleaved signal converters offer significant operational advantages, their realization has often been structurally complex and expensive.